From c4fc256c19dabbb002c5393a8d3548b26efe953f Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Sun, 29 Dec 2019 12:52:37 +0100
Subject: [PATCH] Added tool to warp tiles.

---
 cmd/tilewarp/tilewarp.go | 148 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 cmd/tilewarp/tilewarp.go

diff --git a/cmd/tilewarp/tilewarp.go b/cmd/tilewarp/tilewarp.go
new file mode 100644
index 0000000..ec465f7
--- /dev/null
+++ b/cmd/tilewarp/tilewarp.go
@@ -0,0 +1,148 @@
+package main
+
+import (
+	"image"
+	"image/color"
+	"image/png"
+	"log"
+	"os"
+)
+
+func main() {
+	err := run()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func loadPNG(path string) (image.Image, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	return png.Decode(f)
+}
+
+func storePNG(path string, im image.Image) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return png.Encode(f, im)
+}
+
+type warpFn func(image.Image) image.Image
+
+func warp(path string, warp warpFn) error {
+	im, err := loadPNG(path)
+	if err != nil {
+		return err
+	}
+	warped := warp(im)
+	return storePNG(path, warped)
+}
+
+type warpTile struct {
+	im image.Image
+
+	right    int
+	farRight int
+	top      int
+	farTop   int
+
+	src tile
+	dst tile
+
+	yOffset int
+}
+
+type tile struct {
+	width  int
+	height int
+}
+
+func (w warpTile) ColorModel() color.Model { return w.im.ColorModel() }
+
+func (w warpTile) Bounds() image.Rectangle {
+	bounds := w.im.Bounds()
+	bounds.Max.Y = bounds.Dy() * w.dst.height / w.src.height
+	return bounds
+}
+
+func (w warpTile) At(x, y int) color.Color {
+	offset := image.Point{}
+	for x >= w.dst.width {
+		x -= w.dst.width
+		offset.X += w.src.width
+	}
+	for y >= w.dst.height {
+		y -= w.dst.height
+		offset.Y += w.src.height
+	}
+	y += w.yOffset
+
+	if y >= w.top && x < w.right {
+		return w.im.At(x+offset.X, y-6*30+offset.Y)
+	}
+
+	isTopSide := func() bool {
+		if y >= w.top {
+			return false
+		}
+		if x < w.right {
+			return true
+		}
+		sideX := w.farRight - (w.farRight-w.right)*(y-w.farTop)/(w.top-w.farTop)
+		return x < sideX
+	}
+	if isTopSide() {
+		srcY := w.farTop + (6*40)*(y-w.farTop)/(w.top-w.farTop)
+		return w.im.At(x+offset.X, srcY+offset.Y)
+	}
+	srcY := y - (6*30)*(w.farRight-x)/(w.farRight-w.right)
+	srcBottom := 6 * 160
+	if srcY > srcBottom {
+		srcY = srcBottom
+	}
+	return w.im.At(x+offset.X, srcY+offset.Y)
+}
+
+func run() error {
+	warp("../krampus19/res/tile_lava_brick.png", func(im image.Image) image.Image {
+		return &warpTile{
+			im:       im,
+			dst:      tile{width: 6 * 170, height: 6 * 190},
+			src:      tile{width: 6 * 170, height: 6 * 160},
+			right:    6 * 110,
+			farRight: 6 * 160,
+			top:      6 * 80,
+			farTop:   6 * 10,
+		}
+	})
+	warp("../krampus19/res/tile_magma.png", func(im image.Image) image.Image {
+		return &warpTile{
+			im:       im,
+			dst:      tile{width: 6 * 170, height: 6 * 190},
+			src:      tile{width: 6 * 170, height: 6 * 160},
+			right:    6 * 110,
+			farRight: 6 * 160,
+			top:      6 * 100,
+			farTop:   6 * 30,
+		}
+	})
+	warp("../krampus19/res/entity_brick.png", func(im image.Image) image.Image {
+		return &warpTile{
+			im:       im,
+			dst:      tile{width: 6 * 170, height: 6 * 190},
+			src:      tile{width: 6 * 170, height: 6 * 160},
+			yOffset:  18,
+			right:    6 * 100,
+			farRight: 6 * 150,
+			top:      6 * 100,
+			farTop:   6 * 30,
+		}
+	})
+	return nil
+}